[kip51035]

a little over three years ago I purchased a Y&S .91 4S (supercharged) engine off of ebay. It is in really good shape. I finally got around to running it today. I wanted to set it up before I put it in an aircraft. I was using 4s fuel 15% nitro and a fox R/C plug. It vibrates pretty good at full throttle, I got the mid range set and the low speed. It has a very low idle and good transition all the way up, BUT at 1/3rd throttle there is bubbles in the line from the regulator to the carb and if I leave it there the engine loads up and goes quite rich. Every where else it runs perfect. Has anyone mounted one of these on one of those shock absorbing mounts? Do they help or make things worse?

Kip

[Ron Kennedy]

The YS was one of the strongest of the engines in that range that we used in our pattern ships a few years back.
On later models of the YS they used darker fuel line so people wouldn't see the bubbles.
I was told that it is normal.
If you can't get it to lean out a bit at 1 to 1-1/2 turns out on the main needle then you probably have the pump set too rich.
The soft mount- such as the Hyde mount- will make a huge difference to your servo and battery life,as they don't have to fight to hold neutral against the vibration set up by that much power.
The airframe will last longer as well. Good luck
They also like 20-25% fuel and a good 4-stroke plug.

[ss40a]

OS F plug!
They do OK on 15%